236 



THE AMERICAN ENTOMOLOGIST. 



bred, have come to their growth in about three 

 weeks after hatching. They cast their skius at 

 three successive periods, and these skius are 

 slipped ou to the fork, where in most instances 

 the)' remain. On carefully detaching from a full 

 grown larva the dung with which these skins are 

 mixed, these three successive skius are easily 

 recoguized, the smallest being at the extremity 

 and the largest at the base of the fork. They are 

 especially recognizable in the mottled species 

 {Cassida guttata, Oliv., Fig. 179) mentioned be- 

 low, which removes most of its dung before 

 each moult. 



The eggs from which these larv« hatch, and 

 which we do not recollect to have seen any- 

 where described, are deposited singly upon the 

 leaves, to which they are fastened b)* some ad- 



[Pjg. 175.] 



hesive substance. They are 

 of irregular angular form; 

 flat, and somewhat narrower 

 at one end than the other; 

 ridged above and at the 

 sides, but smooth and obo- 

 vate below. They are usu- 

 ally furnished with si^ine- 

 like appendages, which how- 

 ever are sometimes entirely 

 lacking. Those of C. auri- 

 chalcea (Fig. 176) are 0.04 

 Color— Dirty- white, inch long, and of a dull 

 dirty-white color. 



When full grown the larvae fasten the last 

 two or three joints of the body to the underside 

 of a leaf, by means of a sticky secretion, and in 

 about two days change to pups. The pupa is 

 also flat with usually four or five broad but thin 

 and transparent serrated leaf-like appendages ou 

 each side of the abdomen, and the prothorax 

 which is greatly dilated and covers the head, is 

 furnished around the edge with smaller barbed 

 spines. The broad leaf-like spines at the edges 

 of the body are bent under while the transfor- 

 mation is being effected, but are soon afterwards 

 stretched stiffly out with a forward slant. The 

 pupa loses the pronged tail, but as the old larval 

 skin is left adhering to the terminal segments 

 the prong of dung still protects it in most cases. 

 The legs and antennas are not free in this, as in 

 the pupae of most other beetles, but are soldered 

 together as in the chrysalis of a butterfly, and 

 yet it has the power of raising itself up jierpen- 

 dicularly upon the tail end by which it is fas- 

 tened. The pupa state lasts about a week. 

 \ Having thus spoken in general terms of this 

 anomalous group of beetles, we shall now refer 

 more particularly to a few of the species. Most 

 of those mentioned below infest the Sweet-po- 



tato both in the larva and perfect beetle states. 

 They gnaw irregular holes and when sufla.ciently 

 numerous entirely riddle the leaves. They 

 usually dwell on the underside of the leaves, 

 and are found most abundant during the months 

 of May and June. There must be several 

 broods during the year, and the same species is 

 often found in all stages, and of all sizes at one 

 and the same time. In all probability they 

 hybernate in the beetle state. 



We have already proved b}' experiment that 

 Paris green — one part of the green to two of 

 flour — when sprinkled under the vines, will 

 kill these insects, though not near so readily as 

 it does the Colorado Potato Bug. Moreover, as 

 these Tortoise-beetles usually hide on the under 

 side of the leaves, and as the vines trail on the 

 ground, it is very diflicult to apply the powder 

 without ruianing some risk from its poisonous 

 qualities. We therefore strongly recommend 

 vigilance when the plants are flrst planted, and 

 by the figures and descriptions given below our 

 readers will be enabled to recognize and kill 

 the few beetles which at that time make their 

 appearance, and thus nip the evil in the bud. 



The Two-striped Sweet-potato Beetle. 



[Gassida iveittata, Say.) 

 This is the most common species fouud upon 

 the Sweet-potato, and seems to be confined to 

 [Fig. 176.] that plant, as we have 



never found it on any 

 other kind. Its trans- 

 lormations were first 

 ilescribedby the Junior 

 Editor in the Prairie 

 Farmer Annual, for 

 1868, (p. 53.) The 

 larva (Fig. 174, 2 enlarged; Fig. 176, natural 

 size), is dirty-white or yellowish-white, with a 

 more or less intense neutral-colored longitudinal 

 line along the back, usually relieved by an extra 

 light band each side. It differs from the larvse 

 of all other known species in not using its fork 

 for merdigerous purposes. Indeed, this fork is 

 rendered useless as a shield to the body, by 

 being ever enveloped, after the flrst moult, in 

 the cast-ofi' prickly skins, which are kept free 

 from excrement. Moreover, this fork is seldom 

 held close down to the back, as in the other 

 species, but more usually at an angle of 45° over 

 or from the body, thus suggesting the idea of a 

 handle. In Kirby & Spence's Introduction (p. 

 426), may be found the following passage in 

 reference to the positions in which the fork 

 of the larvse of these Tortoise-beetles is car- 

 ried. "The instrument by which they effect 



L 



Coloi^— Black audvellow 



